With the realization that end of scaling for conventional CMOS integrated circuits is fast approaching in the semiconductor industry, alternative nanostructures and materials have been investigated. Of such nanostructures and materials, carbon nanotubes (CNTs) offer excellent intrinsic properties that are suitable for high performance nanoscale devices. Research in the replacement of semiconductor based field effect transistors and optoelectronic devices and sensors with carbon nanotube based nanoscale devices has been producing promising results in this field.
A key advantage of CNTs over conventional CMOS devices is that scaling limitations of MOSFETs due to boundary scattering of electrons from imperfect interfaces are solved naturally in CNTs which have a smooth, well coordinated graphene structure with no bonds to the outside. This enables CNTs to retain excellent transport properties to much smaller lateral dimensions than silicon. The small radius and possibility of completely surrounding the CNT by a gate provide excellent electrostatic confinement of channel electrons, enabling the channel length to be scaled down to very small dimensions, and their small size would enable high packing densities.
Although single, isolated CNT based field effect transistors and other devices have been demonstrated, many challenges remain in the construction of an integrated circuit employing CNTs as an active material. One such challenge is reliable placement of CNTs on a substrate surface with alignment, i.e., placement of the CNTs in a predefined region for fabrication of a CNT based device.
Several methods for selective placement of CNTs on a surface have been disclosed in the prior art. An exemplary prior art method employs the steps of:
prepatterning the surface into a metal oxide region and a silicon oxide region;
applying alkylphosphonic acids or alkylhydroxamic acids on the prepatterned surface, wherein the alkylphosphonic acids or alkylhydroxamic acids self-assemble on the silicon oxide region, while not assembling on the metal oxide region; and
applying functionalized CNTs on the prepatterned surface containing the patterned alkylphosphonic acids or alkylhydroxamic acids, wherein the functionalized CNTs are selectively attracted to the metal oxide region.
The exemplary prior art method has the drawback of requiring at least one lithographic step for formation of the metal oxide region and the silicon oxide region, in which a photoresist needs to be applied directly on the surface to be patterned, thus making the cleaning of residual photoresist material from the surface difficult and thereby degrading the effectiveness and fidelity of the pattern to be formed on the surface.
In view of the above, there exists a need for a method for patterning a surface into hydrophobic regions and hydrophilic regions without direct contact of a photoresist with the surface so that residual material from the photoresist does not produce adverse effects on the pattern, and a chemical compound for effecting such a method.